Entrapment of chlorophyll from Chlorella vulgaris and Chlorella protothecoides into microporous silica synthesized by a sol-gel method

Abstract

This study presents results of the preparation, absorption and emission characterizations of chlorophyll samples extracted from green microalgae, based on the importance of this pigment and its optical properties. In this work, we characterized extracts containing chlorophyll from green microalgae of the genus Chlorella (C. vulgaris and C. protothecoides) via absorption and emission spectroscopies. The present results were compared with those of chlorophyll extracted from grass, previously reported. Microalgal chlorophyll samples were covalently bonded to the pore surface of organo-modified silica xerogels for a major spectroscopic analysis. Our findings indicate that the composition of green microalgal extracts corresponds mainly to chlorophyll a with a minimal amount of β-carotene. UV-VIS, IR absorption and UV-VIS emission spectra of the samples displayed the typical bands of chlorophyll a, and some other bands ascribed to β-carotene. Both the obtained absorption and emission spectra identify the algae chlorophyll bands and are unique. An effect of a radiative energy transfer mechanism between the silica matrix and the microalgal chlorophyll was observed as reabsorption bands in the emission spectra, and this effect was more evident in the C. vulgaris sample with respect to C. protothecoides.